Utility lines for water, electricity, gas, telephone, cable television, fiber optics, and the like are often run underground for reasons of safety and aesthetics. Sometimes, the underground utilities are buried in a trench that is then backfilled. However, trenching can be time consuming and can cause substantial damage to existing structures or roadways. As an alternative, underground drilling processes and systems have been developed for installing utilities underground. A common underground drilling process involves initially drilling a pilot bore from a launch point to a termination point. Once the pilot bore has been drilled, the pilot bore can be enlarged using a back reaming process. During back reaming, a product (e.g., a pipe) can be pulled behind the back reamer into the back reamed hole. For some drilling techniques, the launch point and the termination point can be below-ground (e.g., in pits). Other drilling techniques can have the launch and termination points at ground level. For this type of drilling process, the drilled bore often defines a curved path which angles into the ground from the launch point and gradually curves upwardly to reach the termination point. Known techniques can be used for steering the drilling machine during drilling so that the drilled bore follows a desired path. Relatively long bores can be drilled by coupling a relatively large number of drill rods together to form a drill string.
One type of directional drilling machine includes an elongate track (e.g., a rack) that can be aligned at an inclined orientation relative to the ground. A rotational driver (e.g., a gear box) is mounted on the track (e.g., by a carriage) so as to be movable along a drive axis that extends parallel to the length of the track. In certain examples, a rack and pinion drive is used to propel the rotational driver along the track. The rotational driver can include a drive member that is rotated by the rotational driver about the drive axis. The drive member is adapted for connection to a drill rod (e.g., a drill pipe). The drill rod can have a threaded end including either female or male threads.
To drill a bore using a directional drilling machine of the type described above, the track is oriented at an inclined angle relative to the ground, and the rotational driver is moved to an upper end of the track. Next, a drill rod is unloaded from a drill rod storage structure (e.g., a magazine) of the directional drilling machine and an upper end of the drill rod is coupled to the drive member of the rotational driver typically by a threaded connection. After the upper end of the drill rod has been coupled to the rotational driver, the lower end of the drill rod is coupled to a drill head if the drill rod is the first drill rod to be introduced into the ground, or to the upper-most drill rod of an existing drill string if the drill string has already been started. Thereafter, the rotational driver is driven in a downward direction along the inclined track while the drive member is concurrently rotated about the drive axis. As the rotational driver is driven down the track, the rotational driver transfers axial thrust and torque to the drill string. The axial thrust and torque is transferred through the drill string to the drill head thereby causing a cutting element (e.g., a bit) of the drill head to rotationally bore through the ground. The length of the bore is progressively increased as drill rods are progressively added to the drill string. The drill rods are most commonly secured together by threaded connections at joints between the drill rods.
After a bore has been drilled, it is necessary to pull back the drill string to remove the drill string from the bore. During the pull-back process, drill rods of the drill string are individually withdrawn from the ground, uncoupled from the drill string, and returned to the drill rod storage structure. Often, back reaming is done as part of the pull-back process. To uncouple a withdrawn drill rod from the remainder of the drill string, the threaded coupling between the withdrawn drill rod and the subsequent drill rod of the drill string is required to be broken before the withdrawn drill rod can be returned to the rod storage structure. Due to the torque loads associated with drilling and back reaming, threaded couplings between drill rods of a drill string can become quite tight and difficult to break.
Drilling machines have incorporated components and features for increasing efficiency relating to drill rod handling and relating to breaking and making joints. For example, linear and/or pivotal rod handling devices can be provided on drilling machines for moving drill rods between a rod storage structure and a drive axis of a rotational driver. Example rod handling devices are disclosed by U.S. Pat. Nos. 5,556,253; 5,607,280; 6,332,502; and 6,543,551. Also, one or more vises can be provided on the drilling machine for facilitating making and breaking threaded joint connections. Example vise arrangements for use with drilling machines are disclosed by U.S. Pat. No. 9,598,905; U.S. Patent Application Publication No. US 2009/0095526; and PCT Publication No. WO 2017/020008. Further, systems for applying a lubricant such as grease to the threaded joints of drill rods have been developed to facilitate breaking joints after drilling. U.S. Pat. No. 6,550,547 discloses a system on a drilling machine for applying grease to the threaded ends of drill rods.
Directional drilling machines can use different styles of drilling rods. One style of drilling rod includes a single pipe. In use, the single pipes are strung together and used to rotate a drilling bit at the downward end of the drill string. The drilling bit can include a steering face that is manipulated to steer the drill string. Another style of drill rod includes an inner pipe positioned within an outer pipe. This type of system is disclosed by U.S. Pat. No. 9,598,905, which is hereby incorporated by reference in its entirety. When dual-pipe style drilling rods are strung together, the resultant drill string includes inner and outer drill string sections that can be rotated independently, commonly, the inner drill string section can be used to rotate a drill bit while the outer drill string section can be used to control the position or orientation of a steering feature of the drill string.
Regardless of the type of drill rod used, efficiency is an important aspect of the operation of any drilling machine. In this regard, the ability to efficiently make and break joints between drill rods is an important efficiency consideration. Wear reduction is another important consideration in the design of drilling machines.